/**
 * @file
 *
 * Transmission Control Protocol for IP
 *
 * This file contains common functions for the TCP implementation, such as functinos
 * for manipulating the data structures and the TCP timer functions. TCP functions
 * related to input and output is found in tcp_in.c and tcp_out.c respectively.
 *
 */

/*
 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * This file is part of the lwIP TCP/IP stack.
 *
 * Author: Adam Dunkels <adam@sics.se>
 *
 */

#include <string.h>

#include "lwip/opt.h"
#include "lwip/def.h"
#include "lwip/mem.h"
#include "lwip/memp.h"

#include "lwip/tcp.h"
#if LWIP_TCP

/* Incremented every coarse grained timer shot
   (typically every 500 ms, determined by TCP_COARSE_TIMEOUT). */
u32_t tcp_ticks;
const u8_t tcp_backoff[13] =
        {
                1, 2, 3, 4, 5, 6, 7, 7, 7, 7, 7, 7, 7
        };

/* The TCP PCB lists. */

/** List of all TCP PCBs in LISTEN state */
union tcp_listen_pcbs_t tcp_listen_pcbs;
/** List of all TCP PCBs that are in a state in which
 * they accept or send data. */
struct tcp_pcb *tcp_active_pcbs;
/** List of all TCP PCBs in TIME-WAIT state */
struct tcp_pcb *tcp_tw_pcbs;

struct tcp_pcb *tcp_tmp_pcb;

static u8_t tcp_timer;
static u16_t tcp_new_port(void);

/**
 * Initializes the TCP layer.
 */
void tcp_init(void)
{
        /* Clear globals. */
        tcp_listen_pcbs.listen_pcbs = NULL;
        tcp_active_pcbs = NULL;
        tcp_tw_pcbs = NULL;
        tcp_tmp_pcb = NULL;

        /* initialize timer */
        tcp_ticks = 0;
        tcp_timer = 0;
        sysSetTimerEvent(TIMER0, TCP_TMR_INTERVAL/10, (PVOID)tcp_tmr);
}

/**
 * Called periodically to dispatch TCP timers.
 *
 */
void tcp_tmr(void)
{
        /* Call tcp_fasttmr() every 250 ms */
        tcp_fasttmr();

        if (++tcp_timer & 1) {
                /* Call tcp_tmr() every 500 ms, i.e., every other timer
                   tcp_tmr() is called. */
                tcp_slowtmr();
        }
       // sysSetTimerEvent(TIMER0, TCP_TMR_INTERVAL/10, (PVOID)tcp_tmr);        
}

/**
 * Closes the connection held by the PCB.
 *
 */
err_t tcp_close(struct tcp_pcb *pcb)
{
        err_t err;
        SYS_ARCH_DECL_PROTECT(old_level);
        SYS_ARCH_PROTECT(old_level);        
#if TCP_DEBUG
        LWIP_DEBUGF(TCP_DEBUG, ("tcp_close: closing in state "));
        tcp_debug_print_state(pcb->state);
        LWIP_DEBUGF(TCP_DEBUG, ("\n"));
#endif /* TCP_DEBUG */
        switch (pcb->state)
        {
        case CLOSED:
                /* Closing a pcb in the CLOSED state might seem erroneous,
                 * however, it is in this state once allocated and as yet unused
                 * and the user needs some way to free it should the need arise.
                 * Calling tcp_close() with a pcb that has already been closed, (i.e. twice)
                 * or for a pcb that has been used and then entered the CLOSED state 
                 * is erroneous, but this should never happen as the pcb has in those cases
                 * been freed, and so any remaining handles are bogus. */
                err = ERR_OK;
                memp_free(MEMP_TCP_PCB, pcb);
                pcb = NULL;
                break;
        case LISTEN:
                err = ERR_OK;
                tcp_pcb_remove((struct tcp_pcb **)&tcp_listen_pcbs.pcbs, pcb);
                memp_free(MEMP_TCP_PCB_LISTEN, pcb);
                pcb = NULL;
                break;
        case SYN_SENT:
                err = ERR_OK;
                tcp_pcb_remove(&tcp_active_pcbs, pcb);
                memp_free(MEMP_TCP_PCB, pcb);
                pcb = NULL;
                break;
        case SYN_RCVD:
        case ESTABLISHED:
                err = tcp_send_ctrl(pcb, TCP_FIN);
                if (err == ERR_OK) {
                        pcb->state = FIN_WAIT_1;
                }
                break;
        case CLOSE_WAIT:
                err = tcp_send_ctrl(pcb, TCP_FIN);
                if (err == ERR_OK) {
                        pcb->state = LAST_ACK;
                }
                break;
        default:
                /* Has already been closed, do nothing. */
                err = ERR_OK;
                pcb = NULL;
                break;
        }

        if (pcb != NULL && err == ERR_OK)
        {
                err = tcp_output(pcb);
        }
        SYS_ARCH_UNPROTECT(old_level);        
        return err;
}

/**
 * Aborts a connection by sending a RST to the remote host and deletes
 * the local protocol control block. This is done when a connection is
 * killed because of shortage of memory.
 *
 */
void tcp_abort(struct tcp_pcb *pcb)
{
        u32_t seqno, ackno;
        u16_t remote_port, local_port;
        struct ip_addr remote_ip, local_ip;
#if LWIP_CALLBACK_API
        void (* errf)(void *arg, err_t err);
#endif /* LWIP_CALLBACK_API */
        void *errf_arg;

        SYS_ARCH_DECL_PROTECT(old_level);
        SYS_ARCH_PROTECT(old_level); 

        /* Figure out on which TCP PCB list we are, and remove us. If we
           are in an active state, call the receive function associated with
           the PCB with a NULL argument, and send an RST to the remote end. */
        if (pcb->state == TIME_WAIT)
        {
                tcp_pcb_remove(&tcp_tw_pcbs, pcb);
                memp_free(MEMP_TCP_PCB, pcb);
        } else
        {
                seqno = pcb->snd_nxt;
                ackno = pcb->rcv_nxt;
                ip_addr_set(&local_ip, &(pcb->local_ip));
                ip_addr_set(&remote_ip, &(pcb->remote_ip));
                local_port = pcb->local_port;
                remote_port = pcb->remote_port;
#if LWIP_CALLBACK_API
                errf = pcb->errf;
#endif /* LWIP_CALLBACK_API */
                errf_arg = pcb->callback_arg;
                tcp_pcb_remove(&tcp_active_pcbs, pcb);
                if (pcb->unacked != NULL) {
                        tcp_segs_free(pcb->unacked);
                }
                if (pcb->unsent != NULL) {
                        tcp_segs_free(pcb->unsent);
                        //sysprintf("!!\n");
                }
#if TCP_QUEUE_OOSEQ
                if (pcb->ooseq != NULL) {
                        tcp_segs_free(pcb->ooseq);
                }
#endif /* TCP_QUEUE_OOSEQ */
                memp_free(MEMP_TCP_PCB, pcb);
                TCP_EVENT_ERR(errf, errf_arg, ERR_ABRT);
                LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_abort: sending RST\n"));
                tcp_rst(seqno, ackno, &local_ip, &remote_ip, local_port, remote_port);
        }
        SYS_ARCH_UNPROTECT(old_level);                                
        
}

/**
 * Binds the connection to a local portnumber and IP address. If the
 * IP address is not given (i.e., ipaddr == NULL), the IP address of
 * the outgoing network interface is used instead.
 *
 */

err_t tcp_bind(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port)
{
        struct tcp_pcb *cpcb;

        if (port == 0)
        {
                port = tcp_new_port();
        }
        /* Check if the address already is in use. */
        for (cpcb = (struct tcp_pcb *)tcp_listen_pcbs.pcbs;
                        cpcb != NULL; cpcb = cpcb->next)
        {
                if (cpcb->local_port == port) {
                        if (ip_addr_isany(&(cpcb->local_ip)) ||
                                        ip_addr_isany(ipaddr) ||
                                        ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
                                return ERR_USE;
                        }
                }
        }
        for (cpcb = tcp_active_pcbs;
                        cpcb != NULL; cpcb = cpcb->next)
        {
                if (cpcb->local_port == port) {
                        if (ip_addr_isany(&(cpcb->local_ip)) ||
                                        ip_addr_isany(ipaddr) ||
                                        ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
                                return ERR_USE;
                        }
                }
        }

        if (!ip_addr_isany(ipaddr))
        {
                pcb->local_ip = *ipaddr;
        }
        pcb->local_port = port;
        LWIP_DEBUGF(TCP_DEBUG, ("tcp_bind: bind to port %"U16_F"\n", port));
        return ERR_OK;
}
#if LWIP_CALLBACK_API
static err_t tcp_accept_null(void *arg, struct tcp_pcb *pcb, err_t err)
{
        (void)arg;
        (void)pcb;
        (void)err;

        return ERR_ABRT;
}
#endif /* LWIP_CALLBACK_API */

/**
 * Set the state of the connection to be LISTEN, which means that it
 * is able to accept incoming connections. The protocol control block
 * is reallocated in order to consume less memory. Setting the
 * connection to LISTEN is an irreversible process.
 *
 */
struct tcp_pcb *tcp_listen(struct tcp_pcb *pcb)
{
        struct tcp_pcb_listen *lpcb;

        /* already listening? */
        if (pcb->state == LISTEN)
        {
                return pcb;
        }
        lpcb = memp_malloc(MEMP_TCP_PCB_LISTEN);
        if (lpcb == NULL)
        {
                return NULL;
        }
        lpcb->callback_arg = pcb->callback_arg;
        lpcb->local_port = pcb->local_port;
        lpcb->state = LISTEN;
        lpcb->so_options = pcb->so_options;
        lpcb->so_options |= SOF_ACCEPTCONN;
        lpcb->ttl = pcb->ttl;
        lpcb->tos = pcb->tos;
        ip_addr_set(&lpcb->local_ip, &pcb->local_ip);
        memp_free(MEMP_TCP_PCB, pcb);
#if LWIP_CALLBACK_API
        lpcb->accept = tcp_accept_null;
#endif /* LWIP_CALLBACK_API */
        TCP_REG(&tcp_listen_pcbs.listen_pcbs, lpcb);
        return (struct tcp_pcb *)lpcb;
}

/**
 * This function should be called by the application when it has
 * processed the data. The purpose is to advertise a larger window
 * when the data has been processed.
 *
 */
void tcp_recved(struct tcp_pcb *pcb, u16_t len)
{
        SYS_ARCH_DECL_PROTECT(old_level);
        SYS_ARCH_PROTECT(old_level);          	
        
        if ((u32_t)pcb->rcv_wnd + len > TCP_WND)
        {
                pcb->rcv_wnd = TCP_WND;
        } else
        {
                pcb->rcv_wnd += len;
        }
        if (!(pcb->flags & TF_ACK_DELAY) &&
                        !(pcb->flags & TF_ACK_NOW))
        {
                /*
                 * We send an ACK here (if one is not already pending, hence
                 * the above tests) as tcp_recved() implies that the application
                 * has processed some data, and so we can open the receiver's
                 * window to allow more to be transmitted.  This could result in
                 * two ACKs being sent for each received packet in some limited cases
                 * (where the application is only receiving data, and is slow to
                 * process it) but it is necessary to guarantee that the sender can
                 * continue to transmit.
                 */
                tcp_ack(pcb);
        } else if (pcb->flags & TF_ACK_DELAY && pcb->rcv_wnd >= TCP_WND/2)
        {
                /* If we can send a window update such that there is a full
                 * segment available in the window, do so now.  This is sort of
                 * nagle-like in its goals, and tries to hit a compromise between
                 * sending acks each time the window is updated, and only sending
                 * window updates when a timer expires.  The "threshold" used
                 * above (currently TCP_WND/2) can be tuned to be more or less
                 * aggressive  */
                tcp_ack_now(pcb);
        }

        LWIP_DEBUGF(TCP_DEBUG, ("tcp_recved: recveived %"U16_F" bytes, wnd %"U16_F" (%"U16_F").\n",
                                len, pcb->rcv_wnd, TCP_WND - pcb->rcv_wnd));
        SYS_ARCH_UNPROTECT(old_level);                                
}

/**
 * A nastly hack featuring 'goto' statements that allocates a
 * new TCP local port.
 */
static u16_t tcp_new_port(void)
{
        struct tcp_pcb *pcb;
#ifndef TCP_LOCAL_PORT_RANGE_START
#define TCP_LOCAL_PORT_RANGE_START 4096
#define TCP_LOCAL_PORT_RANGE_END   0x7fff
#endif
        static u16_t port = TCP_LOCAL_PORT_RANGE_START;

again:
        if (++port > TCP_LOCAL_PORT_RANGE_END) {
                port = TCP_LOCAL_PORT_RANGE_START;
        }

        for (pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
                if (pcb->local_port == port) {
                        goto again;
                }
        }
        for (pcb = tcp_tw_pcbs; pcb != NULL; pcb = pcb->next) {
                if (pcb->local_port == port) {
                        goto again;
                }
        }
        for (pcb = (struct tcp_pcb *)tcp_listen_pcbs.pcbs; pcb != NULL; pcb = pcb->next) {
                if (pcb->local_port == port) {
                        goto again;
                }
        }
        return port;
}

/**
 * Connects to another host. The function given as the "connected"
 * argument will be called when the connection has been established.
 *
 */
err_t tcp_connect(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port,
            err_t (* connected)(void *arg, struct tcp_pcb *tpcb, err_t err))
{
        u32_t optdata;
        err_t ret;
        u32_t iss;
        SYS_ARCH_DECL_PROTECT(old_level);
        SYS_ARCH_PROTECT(old_level);  
        
        LWIP_DEBUGF(TCP_DEBUG, ("tcp_connect to port %"U16_F"\n", port));
        if (ipaddr != NULL)
        {
                pcb->remote_ip = *ipaddr;
        } else
        {
                SYS_ARCH_UNPROTECT(old_level);        	
                return ERR_VAL;
        }
        pcb->remote_port = port;
        if (pcb->local_port == 0)
        {
                pcb->local_port = tcp_new_port();
        }
        iss = tcp_next_iss();
        pcb->rcv_nxt = 0;
        pcb->snd_nxt = iss;
        pcb->lastack = iss - 1;
        pcb->snd_lbb = iss - 1;
        pcb->rcv_wnd = TCP_WND;
        pcb->snd_wnd = TCP_WND;
        pcb->mss = TCP_MSS;
        pcb->cwnd = 1;
        pcb->ssthresh = pcb->mss * 10;
        pcb->state = SYN_SENT;
#if LWIP_CALLBACK_API
        pcb->connected = connected;
#endif /* LWIP_CALLBACK_API */
        TCP_REG(&tcp_active_pcbs, pcb);

        /* Build an MSS option */
        optdata = htonl(((u32_t)2 << 24) |
                        ((u32_t)4 << 16) |
                        (((u32_t)pcb->mss / 256) << 8) |
                        (pcb->mss & 255));

        ret = tcp_enqueue(pcb, NULL, 0, TCP_SYN, 0, (u8_t *)&optdata, 4);
        if (ret == ERR_OK)
        {
                tcp_output(pcb);
        }
        SYS_ARCH_UNPROTECT(old_level);        
        return ret;
}

/**
 * Called every 500 ms and implements the retransmission timer and the timer that
 * removes PCBs that have been in TIME-WAIT for enough time. It also increments
 * various timers such as the inactivity timer in each PCB.
 */
void tcp_slowtmr(void)
{
        struct tcp_pcb *pcb, *pcb2, *prev;
        u32_t eff_wnd;
        u8_t pcb_remove;      /* flag if a PCB should be removed */
        err_t err;

        err = ERR_OK;

        ++tcp_ticks;

        /* Steps through all of the active PCBs. */
        prev = NULL;
        pcb = tcp_active_pcbs;
        if (pcb == NULL) {
                LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: no active pcbs\n"));
        }
        while (pcb != NULL) {
                LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: processing active pcb\n"));
                LWIP_ASSERT("tcp_slowtmr: active pcb->state != CLOSED\n", pcb->state != CLOSED);
                LWIP_ASSERT("tcp_slowtmr: active pcb->state != LISTEN\n", pcb->state != LISTEN);
                LWIP_ASSERT("tcp_slowtmr: active pcb->state != TIME-WAIT\n", pcb->state != TIME_WAIT);

                pcb_remove = 0;

                if (pcb->state == SYN_SENT && pcb->nrtx == TCP_SYNMAXRTX) {
                        ++pcb_remove;
                        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: max SYN retries reached\n"));
                } else if (pcb->nrtx == TCP_MAXRTX) {
                        ++pcb_remove;
                        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: max DATA retries reached\n"));
                } else {
                        ++pcb->rtime;
                        if (pcb->unacked != NULL && pcb->rtime >= pcb->rto) {

                                /* Time for a retransmission. */
                                LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_slowtmr: rtime %"U16_F" pcb->rto %"U16_F"\n",
                                                            pcb->rtime, pcb->rto));

                                /* Double retransmission time-out unless we are trying to
                                 * connect to somebody (i.e., we are in SYN_SENT). */
                                if (pcb->state != SYN_SENT) {
                                        pcb->rto = ((pcb->sa >> 3) + pcb->sv) << tcp_backoff[pcb->nrtx];
                                }
                                /* Reduce congestion window and ssthresh. */
                                eff_wnd = LWIP_MIN(pcb->cwnd, pcb->snd_wnd);
                                pcb->ssthresh = eff_wnd >> 1;
                                if (pcb->ssthresh < pcb->mss) {
                                        pcb->ssthresh = pcb->mss * 2;
                                }
                                pcb->cwnd = pcb->mss;
                                LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_slowtmr: cwnd %"U16_F" ssthresh %"U16_F"\n",
                                                             pcb->cwnd, pcb->ssthresh));

                                /* The following needs to be called AFTER cwnd is set to one mss - STJ */
                                tcp_rexmit_rto(pcb);
                        }
                }
                /* Check if this PCB has stayed too long in FIN-WAIT-2 */
                if (pcb->state == FIN_WAIT_2) {
                        if ((u32_t)(tcp_ticks - pcb->tmr) >
                                        TCP_FIN_WAIT_TIMEOUT / TCP_SLOW_INTERVAL) {
                                ++pcb_remove;
                                LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: removing pcb stuck in FIN-WAIT-2\n"));
                        }
                }

                /* Check if KEEPALIVE should be sent */
                if ((pcb->so_options & SOF_KEEPALIVE) && ((pcb->state == ESTABLISHED) || (pcb->state == CLOSE_WAIT))) {
                        if ((u32_t)(tcp_ticks - pcb->tmr) > (pcb->keepalive + TCP_MAXIDLE) / TCP_SLOW_INTERVAL)  {
                                LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: KEEPALIVE timeout. Aborting connection to %"U16_F".%"U16_F".%"U16_F".%"U16_F".\n",
                                                        ip4_addr1(&pcb->remote_ip), ip4_addr2(&pcb->remote_ip),
                                                        ip4_addr3(&pcb->remote_ip), ip4_addr4(&pcb->remote_ip)));

                                tcp_abort(pcb);
                        } else if ((u32_t)(tcp_ticks - pcb->tmr) > (pcb->keepalive + pcb->keep_cnt * TCP_KEEPINTVL) / TCP_SLOW_INTERVAL) {
                                tcp_keepalive(pcb);
                                pcb->keep_cnt++;
                        }
                }

                /* If this PCB has queued out of sequence data, but has been
                   inactive for too long, will drop the data (it will eventually
                   be retransmitted). */
#if TCP_QUEUE_OOSEQ
                if (pcb->ooseq != NULL &&
                                (u32_t)tcp_ticks - pcb->tmr >=
                                pcb->rto * TCP_OOSEQ_TIMEOUT) {
                        tcp_segs_free(pcb->ooseq);
                        pcb->ooseq = NULL;
                        LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_slowtmr: dropping OOSEQ queued data\n"));
                }
#endif /* TCP_QUEUE_OOSEQ */

                /* Check if this PCB has stayed too long in SYN-RCVD */
                if (pcb->state == SYN_RCVD) {
                        if ((u32_t)(tcp_ticks - pcb->tmr) >
                                        TCP_SYN_RCVD_TIMEOUT / TCP_SLOW_INTERVAL) {
                                ++pcb_remove;
                                LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: removing pcb stuck in SYN-RCVD\n"));
                        }
                }

                /* Check if this PCB has stayed too long in LAST-ACK */
                if (pcb->state == LAST_ACK) {
                        if ((u32_t)(tcp_ticks - pcb->tmr) > 2 * TCP_MSL / TCP_SLOW_INTERVAL) {
                                ++pcb_remove;
                                LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: removing pcb stuck in LAST-ACK\n"));
                        }
                }

                /* If the PCB should be removed, do it. */
                if (pcb_remove) {
                        tcp_pcb_purge(pcb);
                        /* Remove PCB from tcp_active_pcbs list. */
                        if (prev != NULL) {
                                LWIP_ASSERT("tcp_slowtmr: middle tcp != tcp_active_pcbs", pcb != tcp_active_pcbs);
                                prev->next = pcb->next;
                        } else {
                                /* This PCB was the first. */
                                LWIP_ASSERT("tcp_slowtmr: first pcb == tcp_active_pcbs", tcp_active_pcbs == pcb);
                                tcp_active_pcbs = pcb->next;
                        }

                        TCP_EVENT_ERR(pcb->errf, pcb->callback_arg, ERR_ABRT);

                        pcb2 = pcb->next;
                        memp_free(MEMP_TCP_PCB, pcb);
                        pcb = pcb2;
                } else {

                        /* We check if we should poll the connection. */
                        ++pcb->polltmr;
                        if (pcb->polltmr >= pcb->pollinterval) {
                                pcb->polltmr = 0;
                                LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: polling application\n"));
                                TCP_EVENT_POLL(pcb, err);
                                if (err == ERR_OK) {
                                        tcp_output(pcb);
                                }
                        }

                        prev = pcb;
                        pcb = pcb->next;
                }
        }


        /* Steps through all of the TIME-WAIT PCBs. */
        prev = NULL;
        pcb = tcp_tw_pcbs;
        while (pcb != NULL) {
                LWIP_ASSERT("tcp_slowtmr: TIME-WAIT pcb->state == TIME-WAIT", pcb->state == TIME_WAIT);
                pcb_remove = 0;

                /* Check if this PCB has stayed long enough in TIME-WAIT */
                if ((u32_t)(tcp_ticks - pcb->tmr) > 2 * TCP_MSL / TCP_SLOW_INTERVAL) {
                        ++pcb_remove;
                }



                /* If the PCB should be removed, do it. */
                if (pcb_remove) {
                        tcp_pcb_purge(pcb);
                        /* Remove PCB from tcp_tw_pcbs list. */
                        if (prev != NULL) {
                                LWIP_ASSERT("tcp_slowtmr: middle tcp != tcp_tw_pcbs", pcb != tcp_tw_pcbs);
                                prev->next = pcb->next;
                        } else {
                                /* This PCB was the first. */
                                LWIP_ASSERT("tcp_slowtmr: first pcb == tcp_tw_pcbs", tcp_tw_pcbs == pcb);
                                tcp_tw_pcbs = pcb->next;
                        }
                        pcb2 = pcb->next;
                        memp_free(MEMP_TCP_PCB, pcb);
                        pcb = pcb2;
                } else {
                        prev = pcb;
                        pcb = pcb->next;
                }
        }
}

/**
 * Is called every TCP_FAST_INTERVAL (250 ms) and sends delayed ACKs.
 */
void tcp_fasttmr(void)
{
        struct tcp_pcb *pcb;

        /* send delayed ACKs */
        for (pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
                if (pcb->flags & TF_ACK_DELAY) {
                        LWIP_DEBUGF(TCP_DEBUG, ("tcp_fasttmr: delayed ACK\n"));
                        tcp_ack_now(pcb);
                        pcb->flags &= ~(TF_ACK_DELAY | TF_ACK_NOW);
                }
        }
}

/**
 * Deallocates a list of TCP segments (tcp_seg structures).
 *
 */
u8_t tcp_segs_free(struct tcp_seg *seg)
{
        u8_t count = 0;
        struct tcp_seg *next;
        while (seg != NULL)
        {
                next = seg->next;
                count += tcp_seg_free(seg);
                seg = next;
        }
        return count;
}

/**
 * Frees a TCP segment.
 *
 */
u8_t tcp_seg_free(struct tcp_seg *seg)
{
        u8_t count = 0;

        if (seg != NULL)
        {
                if (seg->p != NULL) {
                        count = pbuf_free(seg->p);
#if TCP_DEBUG
                        seg->p = NULL;
#endif /* TCP_DEBUG */
                }
                memp_free(MEMP_TCP_SEG, seg);
        }
        return count;
}

/**
 * Sets the priority of a connection.
 *
 */
void tcp_setprio(struct tcp_pcb *pcb, u8_t prio)
{
        pcb->prio = prio;
}
#if TCP_QUEUE_OOSEQ

/**
 * Returns a copy of the given TCP segment.
 *
 */
struct tcp_seg *tcp_seg_copy(struct tcp_seg *seg)
{
        struct tcp_seg *cseg;

        cseg = memp_malloc(MEMP_TCP_SEG);
        if (cseg == NULL)
        {
                return NULL;
        }
        memcpy((u8_t *)cseg, (const u8_t *)seg, sizeof(struct tcp_seg));
        pbuf_ref(cseg->p);
        return cseg;
}
#endif

#if LWIP_CALLBACK_API
static err_t tcp_recv_null(void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err)
{
        arg = arg;
        if (p != NULL)
        {
                pbuf_free(p);
        } else if (err == ERR_OK)
        {
                return tcp_close(pcb);
        }
        return ERR_OK;
}
#endif /* LWIP_CALLBACK_API */

static void tcp_kill_prio(u8_t prio)
{
        struct tcp_pcb *pcb, *inactive;
        u32_t inactivity;
        u8_t mprio;


        mprio = TCP_PRIO_MAX;

        /* We kill the oldest active connection that has lower priority than
           prio. */
        inactivity = 0;
        inactive = NULL;
        for (pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
                if (pcb->prio <= prio &&
                                pcb->prio <= mprio &&
                                (u32_t)(tcp_ticks - pcb->tmr) >= inactivity) {
                        inactivity = tcp_ticks - pcb->tmr;
                        inactive = pcb;
                        mprio = pcb->prio;
                }
        }
        if (inactive != NULL) {
                LWIP_DEBUGF(TCP_DEBUG, ("tcp_kill_prio: killing oldest PCB %p (%"S32_F")\n",
                                        (void *)inactive, inactivity));
                tcp_abort(inactive);
        }
}


static void tcp_kill_timewait(void)
{
        struct tcp_pcb *pcb, *inactive;
        u32_t inactivity;

        inactivity = 0;
        inactive = NULL;
        for (pcb = tcp_tw_pcbs; pcb != NULL; pcb = pcb->next) {
                if ((u32_t)(tcp_ticks - pcb->tmr) >= inactivity) {
                        inactivity = tcp_ticks - pcb->tmr;
                        inactive = pcb;
                }
        }
        if (inactive != NULL) {
                LWIP_DEBUGF(TCP_DEBUG, ("tcp_kill_timewait: killing oldest TIME-WAIT PCB %p (%"S32_F")\n",
                                        (void *)inactive, inactivity));
                tcp_abort(inactive);
        }
}



struct tcp_pcb *tcp_alloc(u8_t prio)
{
        struct tcp_pcb *pcb;
        u32_t iss;
        
        SYS_ARCH_DECL_PROTECT(old_level);
        SYS_ARCH_PROTECT(old_level);  
        
        pcb = memp_malloc(MEMP_TCP_PCB);
        if (pcb == NULL)
        {
                /* Try killing oldest connection in TIME-WAIT. */
                LWIP_DEBUGF(TCP_DEBUG, ("tcp_alloc: killing off oldest TIME-WAIT connection\n"));
                tcp_kill_timewait();
                pcb = memp_malloc(MEMP_TCP_PCB);
                if (pcb == NULL) {
                        tcp_kill_prio(prio);
                        pcb = memp_malloc(MEMP_TCP_PCB);
                }
        }
        
        SYS_ARCH_UNPROTECT(old_level); 
        
        if (pcb != NULL)
        {
                memset(pcb, 0, sizeof(struct tcp_pcb));
                pcb->prio = TCP_PRIO_NORMAL;
                pcb->snd_buf = TCP_SND_BUF;
                //sysprintf("set qlen 0\n");
                pcb->snd_queuelen = 0;
                pcb->rcv_wnd = TCP_WND;
                pcb->tos = 0;
                pcb->ttl = TCP_TTL;
                pcb->mss = TCP_MSS;
                pcb->rto = 3000 / TCP_SLOW_INTERVAL;
                pcb->sa = 0;
                pcb->sv = 3000 / TCP_SLOW_INTERVAL;
                pcb->rtime = 0;
                pcb->cwnd = 1;
                iss = tcp_next_iss();
                pcb->snd_wl2 = iss;
                pcb->snd_nxt = iss;
                pcb->snd_max = iss;
                pcb->lastack = iss;
                pcb->snd_lbb = iss;
                pcb->tmr = tcp_ticks;

                pcb->polltmr = 0;

#if LWIP_CALLBACK_API
                pcb->recv = tcp_recv_null;
#endif /* LWIP_CALLBACK_API */

                /* Init KEEPALIVE timer */
                pcb->keepalive = TCP_KEEPDEFAULT;
                pcb->keep_cnt = 0;
        }
        
        return pcb;
}

/**
 * Creates a new TCP protocol control block but doesn't place it on
 * any of the TCP PCB lists.
 *
 * @internal: Maybe there should be a idle TCP PCB list where these
 * PCBs are put on. We can then implement port reservation using
 * tcp_bind(). Currently, we lack this (BSD socket type of) feature.
 */

struct tcp_pcb *tcp_new(void)
{	
        return tcp_alloc(TCP_PRIO_NORMAL);
}

/*
 * tcp_arg():
 *
 * Used to specify the argument that should be passed callback
 * functions.
 *
 */

void tcp_arg(struct tcp_pcb *pcb, void *arg)
{
        pcb->callback_arg = arg;
}
#if LWIP_CALLBACK_API

/**
 * Used to specify the function that should be called when a TCP
 * connection receives data.
 *
 */
void tcp_recv(struct tcp_pcb *pcb,
         err_t (* recv)(void *arg, struct tcp_pcb *tpcb, struct pbuf *p, err_t err))
{
        pcb->recv = recv;
}

/**
 * Used to specify the function that should be called when TCP data
 * has been successfully delivered to the remote host.
 *
 */

void tcp_sent(struct tcp_pcb *pcb,
         err_t (* sent)(void *arg, struct tcp_pcb *tpcb, u16_t len))
{
        pcb->sent = sent;
}

/**
 * Used to specify the function that should be called when a fatal error
 * has occured on the connection.
 *
 */
void tcp_err(struct tcp_pcb *pcb,
        void (* errf)(void *arg, err_t err))
{
        pcb->errf = errf;
}

/**
 * Used for specifying the function that should be called when a
 * LISTENing connection has been connected to another host.
 *
 */
void tcp_accept(struct tcp_pcb *pcb,
           err_t (* accept)(void *arg, struct tcp_pcb *newpcb, err_t err))
{
        ((struct tcp_pcb_listen *)pcb)->accept = accept;
}
#endif /* LWIP_CALLBACK_API */


/**
 * Used to specify the function that should be called periodically
 * from TCP. The interval is specified in terms of the TCP coarse
 * timer interval, which is called twice a second.
 *
 */
void tcp_poll(struct tcp_pcb *pcb,
         err_t (* poll)(void *arg, struct tcp_pcb *tpcb), u8_t interval)
{
#if LWIP_CALLBACK_API
        pcb->poll = poll;
#endif /* LWIP_CALLBACK_API */
        pcb->pollinterval = interval;
}

/**
 * Purges a TCP PCB. Removes any buffered data and frees the buffer memory.
 *
 */
void tcp_pcb_purge(struct tcp_pcb *pcb)
{
        if (pcb->state != CLOSED &&
                        pcb->state != TIME_WAIT &&
                        pcb->state != LISTEN)
        {

                LWIP_DEBUGF(TCP_DEBUG, ("tcp_pcb_purge\n"));

                if (pcb->unsent != NULL) {
                        LWIP_DEBUGF(TCP_DEBUG, ("tcp_pcb_purge: not all data sent\n"));
                }
                if (pcb->unacked != NULL) {
                        LWIP_DEBUGF(TCP_DEBUG, ("tcp_pcb_purge: data left on ->unacked\n"));
                }
#if TCP_QUEUE_OOSEQ /* LW */
                if (pcb->ooseq != NULL) {
                        LWIP_DEBUGF(TCP_DEBUG, ("tcp_pcb_purge: data left on ->ooseq\n"));
                }

                tcp_segs_free(pcb->ooseq);
                pcb->ooseq = NULL;
#endif /* TCP_QUEUE_OOSEQ */
                tcp_segs_free(pcb->unsent);
                tcp_segs_free(pcb->unacked);
                //sysprintf("!!\n");
                pcb->unacked = pcb->unsent = NULL;
        }
}

/**
 * Purges the PCB and removes it from a PCB list. Any delayed ACKs are sent first.
 *
 */
void tcp_pcb_remove(struct tcp_pcb **pcblist, struct tcp_pcb *pcb)
{
        TCP_RMV(pcblist, pcb);

        tcp_pcb_purge(pcb);

        /* if there is an outstanding delayed ACKs, send it */
        if (pcb->state != TIME_WAIT &&
                        pcb->state != LISTEN &&
                        pcb->flags & TF_ACK_DELAY)
        {
                pcb->flags |= TF_ACK_NOW;
                tcp_output(pcb);
        }
        pcb->state = CLOSED;

        LWIP_ASSERT("tcp_pcb_remove: tcp_pcbs_sane()", tcp_pcbs_sane());
}

/**
 * Calculates a new initial sequence number for new connections.
 *
 */
u32_t tcp_next_iss(void)
{
        static u32_t iss = 6510;

        iss += tcp_ticks;       /* XXX */
        return iss;
}

#if TCP_DEBUG || TCP_INPUT_DEBUG || TCP_OUTPUT_DEBUG
void tcp_debug_print(struct tcp_hdr *tcphdr)
{
        LWIP_DEBUGF(TCP_DEBUG, ("TCP header:\n"));
        LWIP_DEBUGF(TCP_DEBUG, ("+-------------------------------+\n"));
        LWIP_DEBUGF(TCP_DEBUG, ("|    %5"U16_F"      |    %5"U16_F"      | (src port, dest port)\n",
                                ntohs(tcphdr->src), ntohs(tcphdr->dest)));
        LWIP_DEBUGF(TCP_DEBUG, ("+-------------------------------+\n"));
        LWIP_DEBUGF(TCP_DEBUG, ("|           %010"U32_F"          | (seq no)\n",
                                ntohl(tcphdr->seqno)));
        LWIP_DEBUGF(TCP_DEBUG, ("+-------------------------------+\n"));
        LWIP_DEBUGF(TCP_DEBUG, ("|           %010"U32_F"          | (ack no)\n",
                                ntohl(tcphdr->ackno)));
        LWIP_DEBUGF(TCP_DEBUG, ("+-------------------------------+\n"));
        LWIP_DEBUGF(TCP_DEBUG, ("| %2"U16_F" |   |%"U16_F"%"U16_F"%"U16_F"%"U16_F"%"U16_F"%"U16_F"|     %5"U16_F"     | (hdrlen, flags (",
                                TCPH_HDRLEN(tcphdr),
                                TCPH_FLAGS(tcphdr) >> 5 & 1,
                                TCPH_FLAGS(tcphdr) >> 4 & 1,
                                TCPH_FLAGS(tcphdr) >> 3 & 1,
                                TCPH_FLAGS(tcphdr) >> 2 & 1,
                                TCPH_FLAGS(tcphdr) >> 1 & 1,
                                TCPH_FLAGS(tcphdr) & 1,
                                ntohs(tcphdr->wnd)));
        tcp_debug_print_flags(TCPH_FLAGS(tcphdr));
        LWIP_DEBUGF(TCP_DEBUG, ("), win)\n"));
        LWIP_DEBUGF(TCP_DEBUG, ("+-------------------------------+\n"));
        LWIP_DEBUGF(TCP_DEBUG, ("|    0x%04"X16_F"     |     %5"U16_F"     | (chksum, urgp)\n",
                                ntohs(tcphdr->chksum), ntohs(tcphdr->urgp)));
        LWIP_DEBUGF(TCP_DEBUG, ("+-------------------------------+\n"));
}

void tcp_debug_print_state(enum tcp_state s)
{
        LWIP_DEBUGF(TCP_DEBUG, ("State: "));
        switch (s) {
        case CLOSED:
                LWIP_DEBUGF(TCP_DEBUG, ("CLOSED\n"));
                break;
        case LISTEN:
                LWIP_DEBUGF(TCP_DEBUG, ("LISTEN\n"));
                break;
        case SYN_SENT:
                LWIP_DEBUGF(TCP_DEBUG, ("SYN_SENT\n"));
                break;
        case SYN_RCVD:
                LWIP_DEBUGF(TCP_DEBUG, ("SYN_RCVD\n"));
                break;
        case ESTABLISHED:
                LWIP_DEBUGF(TCP_DEBUG, ("ESTABLISHED\n"));
                break;
        case FIN_WAIT_1:
                LWIP_DEBUGF(TCP_DEBUG, ("FIN_WAIT_1\n"));
                break;
        case FIN_WAIT_2:
                LWIP_DEBUGF(TCP_DEBUG, ("FIN_WAIT_2\n"));
                break;
        case CLOSE_WAIT:
                LWIP_DEBUGF(TCP_DEBUG, ("CLOSE_WAIT\n"));
                break;
        case CLOSING:
                LWIP_DEBUGF(TCP_DEBUG, ("CLOSING\n"));
                break;
        case LAST_ACK:
                LWIP_DEBUGF(TCP_DEBUG, ("LAST_ACK\n"));
                break;
        case TIME_WAIT:
                LWIP_DEBUGF(TCP_DEBUG, ("TIME_WAIT\n"));
                break;
        }
}

void tcp_debug_print_flags(u8_t flags)
{
        if (flags & TCP_FIN) {
                LWIP_DEBUGF(TCP_DEBUG, ("FIN "));
        }
        if (flags & TCP_SYN) {
                LWIP_DEBUGF(TCP_DEBUG, ("SYN "));
        }
        if (flags & TCP_RST) {
                LWIP_DEBUGF(TCP_DEBUG, ("RST "));
        }
        if (flags & TCP_PSH) {
                LWIP_DEBUGF(TCP_DEBUG, ("PSH "));
        }
        if (flags & TCP_ACK) {
                LWIP_DEBUGF(TCP_DEBUG, ("ACK "));
        }
        if (flags & TCP_URG) {
                LWIP_DEBUGF(TCP_DEBUG, ("URG "));
        }
        if (flags & TCP_ECE) {
                LWIP_DEBUGF(TCP_DEBUG, ("ECE "));
        }
        if (flags & TCP_CWR) {
                LWIP_DEBUGF(TCP_DEBUG, ("CWR "));
        }
}

void tcp_debug_print_pcbs(void)
{
        struct tcp_pcb *pcb;
        LWIP_DEBUGF(TCP_DEBUG, ("Active PCB states:\n"));
        for (pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
                LWIP_DEBUGF(TCP_DEBUG, ("Local port %"U16_F", foreign port %"U16_F" snd_nxt %"U32_F" rcv_nxt %"U32_F" ",
                                        pcb->local_port, pcb->remote_port,
                                        pcb->snd_nxt, pcb->rcv_nxt));
                tcp_debug_print_state(pcb->state);
        }
        LWIP_DEBUGF(TCP_DEBUG, ("Listen PCB states:\n"));
        for (pcb = (struct tcp_pcb *)tcp_listen_pcbs.pcbs; pcb != NULL; pcb = pcb->next) {
                LWIP_DEBUGF(TCP_DEBUG, ("Local port %"U16_F", foreign port %"U16_F" snd_nxt %"U32_F" rcv_nxt %"U32_F" ",
                                        pcb->local_port, pcb->remote_port,
                                        pcb->snd_nxt, pcb->rcv_nxt));
                tcp_debug_print_state(pcb->state);
        }
        LWIP_DEBUGF(TCP_DEBUG, ("TIME-WAIT PCB states:\n"));
        for (pcb = tcp_tw_pcbs; pcb != NULL; pcb = pcb->next) {
                LWIP_DEBUGF(TCP_DEBUG, ("Local port %"U16_F", foreign port %"U16_F" snd_nxt %"U32_F" rcv_nxt %"U32_F" ",
                                        pcb->local_port, pcb->remote_port,
                                        pcb->snd_nxt, pcb->rcv_nxt));
                tcp_debug_print_state(pcb->state);
        }
}

s16_t tcp_pcbs_sane(void)
{
        struct tcp_pcb *pcb;
        for (pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
                LWIP_ASSERT("tcp_pcbs_sane: active pcb->state != CLOSED", pcb->state != CLOSED);
                LWIP_ASSERT("tcp_pcbs_sane: active pcb->state != LISTEN", pcb->state != LISTEN);
                LWIP_ASSERT("tcp_pcbs_sane: active pcb->state != TIME-WAIT", pcb->state != TIME_WAIT);
        }
        for (pcb = tcp_tw_pcbs; pcb != NULL; pcb = pcb->next) {
                LWIP_ASSERT("tcp_pcbs_sane: tw pcb->state == TIME-WAIT", pcb->state == TIME_WAIT);
        }
        return 1;
}
#endif /* TCP_DEBUG */
#endif /* LWIP_TCP */










